Steam-boiler.



E. W. PRATT. STEAM BOILER. APPLICATION FILED J-ULY 23,1912

Patnted No 11, 1913.

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'nnwann w. PRATT, or cnrcaooyrrnmois; nssrsnon, BY DIRECT AND MESNE Assloivmnn'r's, 'ro HIMSELF, AND :0 m

IOWA, raosrnns. v

ICHAELOCONNOR, OF MISSOURI VALLEY,

STEAM-BOILER. 4

Specification of Letters Patent. Patented N 1 1, 1913,

Application filed July 23, 1912. Serial No. 711,015.

' ToaZZ whom it may concern:

Be it known that I, EDWARD W. PRATI', of Oak Park, Chicago, in the county of Cook and in the State of Illinois, have invented a certain new and. useful Improvement in Steam- Boilers, and do hereby declare that the following is a full, clear, and exact description thereof.

The object of my invention has been-to provide an improvement in steam boilers which shall enable the door construction thereof to be made more durable and cheaper and less liable to become incrusted and fouled by impurities in the water, and which shall provide freedom for expansion and contraction of the back sheets of the boiler, thereby rendering them less liable to crack or break; and to such ends my invention conregarded as typical only of many possible embodiments, and my invention is not to be confined thereto.

The rear wall of the locomotive boiler is formed of two flat plates, which are held together against the expansive force of the' steam, by stay bolts. In the drnwings these plates are respectively the door; sheet 1 and the back head 2. In order to'form a door opening through this wall of the fire box, to permit: passing coal to the grates, or'permit an examination of the fire-box, a hole is formedin each of these plates in alinement, a flange is formed on each plate around its hole, and the flanges are fastened together directly or indirectly in any one of several ways and calked to make a water-tight joint. The metal is cooled when the door is opened, and then heated when the door is closed,

causing contraction and expansion, which been partly obviated, prior to my invention,

by -forming' a swelling on the inner face of practice has also involved the use of a considerable number of stay bolts whose use is avoided by my invention, thereby eliminating expense. It is desirable to make the inner or door sheet 1 of. relatively thin sheet metal, so as to permit the heat of the fire to reach the water as eflectively as possible, and to permit expansion and contraction with as little cracking as possible. The outer or back sheet 2 is usually made much thicker than the inner sheet, as the heat-of the fire does not have to pass through it to reach the water.- This use of a thin inner or door sheethas, prior to my invent-ion, required that stay bolts connecting the two sheets be placed close to the door opening.

I have discovered that by slanting the stay bolts outwardly, which are nearest to the door opening, I can secure substantial advantages, which I shall mention after hav-. ing described the construction. In accordance with m invention, the back sheet is provided witli the usual flange 3. The door sheet is provided with a swelling 4 which surrounds the door opening, and such swelling is preferably made large for reasons hereinafter stated. Stay bolts 5 are used to connect the two sheets. I so place the stay bolts 6, which are nearest to the door opening, that they are connected with the back sheet at a point closer to the door opening than to the door sheet, and are slanted outward in the direction considered from the back sheet towardthe door sheet. By slanting these stay bolts outward I am enabled to pass them substantially perpendicularly through the door sheet at the baseof the swelling, so that, although such sheet is made thin, an effective fastening'between the stay bolt and the door sheet is secured. As the back sheet is thicker, I find that no harm results from having the stay bolts inclined as they pass through such sheet. By this construction I am enabled to place the stay bolts in the back sheet at a point nearer the door opening than in the door sheet,

which is necessar because the radius of curvature of the ange in the back'sheet is less than that in the door sheet.

As the swelling 4 is of large radius, I that ample stay is secured by having the stay bolts connect with the door sheet at the base of such swelling, as it permits them to be screwed through the door sheet at ap- 1 proximately right angles. This gives full the two sheets.

threads in this the thinner and weaker of My invention affords the following advantages, among others By being able to place the stay bolts farther from the door opening, I am enabled to make the swelling 4; of larger radius than heretofore, and thus to afford a larger water space. This larger body of water absorbs the heat so as to pre-. vent, to some extent, the variations of temperature when the fire door is opened and closed. A better circulation of water about the door hole is aiforded, thereby preventin mud and scale from lodging or collecting. am enabled to omit several of the stay bolts formerly used around the door holes of boilers, thereby saving the expense of applying them, and also of repairing them, as each stay bolt is liable to leak or break and require attention from time to time. This larger space about the door hole without stay bolts permits the fastening of the two door flanges by rivets,instead of patch-bolts, giving-a much better construction, because formerly it was practically impossible to hold on inner end of the rivets soas to drive them. This slanting of the stay bolts about the door permits them to be screwed through the door sheet I at approximatel right angles, as before stated, giving fu 1 threads.

The removal of stay bolts from the bulge.

or swelling permits the latter to enlarge with the expansion and decrease with the contraction of the metal.

Recent designs of locomotive boilers have shortened the distance between the rigid mud ring 7 and the door hole, and as the mud ring is rigid and comparatively cold, it

forms a pivotal point for contraction and stay bolts connecting said sheets, said stay,

bolts being connected to the outer sheet nearer the door opening than they are to the inner sheet, and being connected to the inner sheet approximate y at the base of said swelling, and whereby they spread apart in a direction considered toward the inner sheet.

In testimony that I claim the foregoing I have hereunto set my hand.

EDWARD W. PRATT.

Witnesses:

J. O. Lrrrnn, L. P. MICHAEL. 

